Abstract

This paper applies a modified ubiquitous joint plane model (Modified Ubi) to describe the mechanical behavior of layered rock masses. The constitutive model is an implicit-continuum based one where the joints are smeared across the rock mass. This modified model concerns not only the strength anisotropy but also it integrates the elastic stiffness anisotropy. Thus, the elastic stress increments and the plastic corrections from the original ubiquitous joint model have been altered. Now, it is possible to simulate the elastic and plastic behavior of transversely isotropic rocks. Modified Ubi is applied to simulate the behavior of the transverse isotropic rock samples in uniaxial compressive loading and triaxial loading tests. The results out of the modified model were compared to the analytical solution from Jaeger and the CANISO model from FLAC 8.0.

1. Introduction

Determining the rock mass properties and expecting its behavior are matter of the modelling of the discontinuities in the rock continua. Because of the complex mechanism of the rock mass which may not be directly predicted using the conventional ways of modeling (such as: closed form solutions or physical modelling); numerical modelling is one of the most trending means to model behavior of rock mass [1]. The condition of the rock mass (such as: excessively fractured or reasonably fractured or intact massive) and the scale of the engineering application (i.e.: layering is significantly smaller or bigger than the scale of the application) affect strongly the optimum approach selection of the applied numerical model, either continuum-based approach or discontinuum-based one [2]. Modelling of layered rock mass is still a point of interest between different computational tools which either consider the joint implicitly (i.e.: FLAC - Ubiquitous joint model) or use the explicit representation of the discontinuities (i.e.: UDEC - Discreet element model) [3]. However, both the computational power and time consumed in calculation limit the usage of such discrete approaches. The accuracy of different implicit joint models has been investigated between both the ubiquitous joint model and Cosserat model [4]. This paper adopts the continuum-based approach to implicitly model an isotropic rock mass (i.e.: smeared joints).

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